Hi Brain
Must leave now! I've spent too much time on this! maybe many false leads but one may be the right one.
I'll leave you with this food for thought!
The Southwark William Hall Hatmaker lead location fits the 1794 first known info of William in Leeds 1795 first mention also this James Hall fits merchants and cloth goods, shop keepers etc-Willaim Hall did travel along way to Cumbria to marry Isabella from Leeds, so coming to Leeds from London is not that unrealistic.
Being a hat maker or milliner is a trade that takes time to learn by apprenticeship and that is a puzzle

but he turned to a Woolstapler merchant similar to this James Hall Southwark.#
Enough to keep you going years.
Hall, Thomas (, hat manufacturer).
Residing at 16 King Street, Sheffield in 1825.
Recorded in: Gells 1825 Directory of Sheffield.
Booker, William (, wholesale and retail grocer).
Residing at 16 King Street, Sheffield in 1825.
Recorded in: Gells 1825 Directory of Sheffield.
Booker, William (, Grocers & Tea Dealers).
Residing at 16 King Street, in 1828-9.
Recorded in: Pigot's Commercial Directory - 1828 to 1829.
Foster, E. (, wholesale grocers and tea dealers, coffee roasters and spice merchants (& C).
Residing at 16 King Street, in 1833.
Recorded in: Whites History & Directory of Sheffield - 1833.
And
http://www.london-gazette.co.uk/issues/18255/pages/1394/page.pdfOFFICE OF THE COURT FOR RELIEF Of
INSOLVENT DEBTOUS
, No..33, Lincoln's
Inn-Fields.PETITIONS of INSOLVENT DEBTORS, to
be heard At Wakefield in the
West Riding of the County of York
http://www.london-gazette.co.uk/issues/18255/pages/1395/page.pdfOn the 28th day of June 1826, at the same
Hour and Place
Thomas Hall, late of Sheffield, Yorkshire, Hatter
.............................................................................................................................
and 1794
Hall William, Wine & Brandy Mercht. 15, Duke street,
Lincoln's inn fieldshttp://www.londonancestor.com/kents/kents-h.htm.........................................................................................................................
http://www.genuki.org.uk/big/eng/YKS/NRY/Malton/Malton23.html1823
Fire, &c. Offices,
County, Thomas, Hall, Yorkersgate
................................................................................................................
1817
Hall, William, hatter & woolstapler & agent to the
London Union Fire Office, 91 Briggate; Hall, Mary, straw hat maker, 91 Briggate
1814 1815 Hat Manufacturers: Hall,
William, 91 Briggate;Woolstapler, Hall,
Thomas, 91 Briggate
Dobby